Printer Ink...why did I never know this: Makes me angry!

[Paper Roses]

I'm not a Staples customer, no real need but I went to pick up something yesterday and found out some interesting information. I have a Canon printer(hate it) # MX492. It eats ink like it was free! In a chat with the very nice clerk about the price of ink, I learned that there is a difference in the packages marked, in my case Canon 245,246.I'm told this situation is the same with all replacement ink.
Unless you buy the printer cartridges marked XL, you are getting an ink cart that is 3/4 full. Those marked XL are full. I feel this is deceitful. No wonder I run out of ink so soon. I don't print often but seem to get no mileage from this product...I've been buying the regular mark, not the XL. I have always bought the manufacturers label, never tried the generic, got them from eBay from a reputable seller in original packages. This stuff is a kings ransom and this printer is awful. My old HP PSC worked far better and was less confusing. When this one dies, I'll go back to an HP and hope for the best. This ink situation really bugs me! AS a P.S. I cannot get the enter or the cursor to allow me to make paragraphs. Sorry.